Fitness of transgenic plants Weediness Marianne SCHIMPL, 9940237

1
Fitness of transgenic plants - Weediness
Marianne SCHIMPL, 9940237

• A.M. Chèvre, F. Eber, A. Baranger and M. Renard
• Gene flow from transgenic crops, Nature 389924
  (1997)
• G. Gueritaine, M. Sester, F. Eber, A.M. Chèvre
  and H. Darmency
• Fitness of backcross six of hybrids between
  transgenic oilseed rape (Brassica napus) and wild
  radish (Raphanus raphanistrum). Molecular
  Ecology 11, 1419-1426 (2002)

2
Transfer of herbicide resistance from oilseed
rape to wild radish?
Brassica napus (oilseed rape) 2n38 Westar
T5 from Aventis CropScience homozygous for the
bar gene which confers resistance to the
herbicide glufosinate
Raphanus raphanistrum (wild radish) 2n18
?
?

• crop ? wild species ? hybrids often show low
  fitness (fertility).
• fertility was initially very low (28), but
  improved with every generation, as the progeny
  increasingly ressembled wild radish
• two types of backcross 6
• oilseed rape backcross (oilseed rape cytoplasm
  radish pollen)
• radish backcross
• but what about the herbicide resistance of the
  progeny?

3
presence of the transgene (bar) in backcross 6

• experimental partherbicide resistance was
  determined by spraying the plants with
  glufosinate ammonium-solution at the four-leaf
  stage.The transgene was also detected by PCR.
• result

oilseed rape seedling at the four-leaf stage
The average frequency of resistant plants was
10, not 50 as might be expected for a dominant
Mendelian trait! ? 1 remnant oilseed rape
chromosome is transmitted irregularly
4
results in brief

• the remnant oilseed rape chromosome (not the
  transgene!) is responsible for 10 lower rate
  of flowering plants 50 decreased pollen
  fertility 22 less seed output
• the escape of transgenes into the wild radish
  genome constitutes a major threat
• if the herbicide is applied persistantly the
  selective advantage of transgenic radishes could
  easily compensate the above drawbacks,
  leading to field infestation with resistant
  weeds.

5
Thank you for your attention!